The influence of parent concrete and milling intensity on the properties of recycled aggregates

The C2CA concrete recycling process consists of a combination of smart demolition, gentle grinding of the crushed concrete in an autogenous mill, and a novel dry classification technology called ADR to remove the fines. The` main factors in the C2CA process which influence the properties of Recycled Aggregates or Recycled Aggregate Concrete (RAC) include the type of Parent Concrete (PC), the intensity of autogenous milling and ADR cut-size point. This study aims to investigate the influence of PC and intensity of the autogenous milling on the quality of the produced recycled aggregates. Three types of concrete which are frequently demanded in the Dutch market were cast as PC and their fresh and hardened properties were tested. After near one year curing of PC samples, they were recycled independently while the aforementioned recycling factors were varied. The effects of different recycling variables on the water absorption, density, crushing resistance and durability of produced recycled aggregates were investigated. According to the results, type of the parent concrete is the predominant factor influencing the properties of the recycled aggregates. Milling intensity was found to be effective on improving the properties of recycled aggregates coming from weaker parent concrete. The experimental results suggest that among various milling intensities, milling at medium shear and medium compression improves the overall quality of RA